The analysis of DNA has become vital in modern molecular biology and clinical diagnostics. It is now routine for patients with HIV to have their viral isolates analyzed by DNA sequencing for the presence of mutations that cause drug resistance (“genotyping”). Because the amount of DNA found in biological samples is often below detection by commonly used methods, amplification by polymerase chain reaction (PCR) is utilized to not only increase the amount of DNA but to do so specifically—i.e., targets in a heterogeneous mixture of DNAs are specifically amplified with PCR. Although PCR is highly sensitive, successful application of this procedure to detect single molecules of DNA under ideal conditions requires the use of extensive purification of DNA, use of enzymatic manipulations requiring high levels of expertise, and additional downstream manipulations that can be costly and time-consuming to perform because of technical requirements. Many of these procedures are limited to use as research tools because their application for genetic screening is difficult to implement commercially. The Inventor has discovered a method to detect biological targets including specific DNA targets at ultra-high sensitivity using biolayer interferometry. Because of this high sensitivity, the method circumvents the need for PCR amplification of DNA for many applications related to genetic screening. Whereas conventional biolayer interferometry is capable of detecting ˜0.2 pmole of DNA, the Inventor has extended that sensitivity >1 million-fold so that ˜0.2 attomole (˜100,000) DNA targets are detectable. The method which the Inventor has designated Peroxidase Chain Reaction (PxCR), is able to detect as few as 100 DNA, RNA, and protein targets.